Disc cutter for boring-type mining machine

ABSTRACT

A cutter tool for an earth-boring machine comprises a disc or ring of a metal or alloy having a Rockwell C hardness of at least 60 and having a circumferential cutting edge on its outside surface. The inner surface of the ring, or of a steel liner on which the hard metal ring is mounted, has a tapered crosssectional configuration. A first annular support engages one of the inner tapered surfaces and a second annular support the other tapered surface. These annular supports may be drawn toward each other to exert a hoop stress on the hard metal ring thereby placing it in a prestressed condition. The hard metal ring, its optional steel liner and the supports constitute an assembly which is rotatably mounted on a shaft. The shaft includes means for attachment to an earth-boring machine with the shaft in axial alignment with a radius of the bore.

United States Patent [1 1 Bower, Jr.

[ Oct. 23, 1973 DISC CUTTER FOR BORING-TYPE MINING MACHINE I lnventor: Arnold Boyd Bower, Jr., St. Clair Shores, Mich.

Assignee: General Electric Company, New

York, N.Y. 1

Filed: July 17, 1972 Appl. No.: 272,409

U.S. Cl 175/373, 175/372, 175/374 Int. Cl. E21b 9/14, E2lc 13/00 Field of Search ..175/37l-374,35l,

References Cited UNITED STATES PATENTS 11/1965 Robbins et a1 175/372 X 10/1971 Dixon 7/1972 Goodfellow 175/372 X Primary Examiner-David H. Brown Attorney-Allard A. Braddock et al.

[57] ABSTRACT A cutter tool for an earth-boring machine comprises a disc or ring of a metal or alloy having a Rockwell C hardness of at least 60 and having a circumferential cutting edge on its outside surface. The inner surface of the ring, or of a steel liner on which the hard metal ring is mounted, has a tapered cross-sectional configuration. A first annular support engages one of the inner tapered surfaces and a second annular support the other tapered surface. These annular supports may be drawn toward each other to exert a hoop stress on the hard metal ring thereby placing it in a prestressed condition. The hard metal ring, its optional steel liner and the supports constitute an assembly which is rotatably mounted on a shaft. The shaft includes means for attachment to an earth-boring machine with the shaft in axial alignment with a radius of the bore.

6 Claims, 2 Drawing Figures DISC CUTTER FOR BORING-TYPE MINING MACHINE BACKGROUND OF THE INVENTION Machines of the type for boring large-diameter tunnels of the type used for transporting water, sewage, traffic, etc., are disclosed in US. Pat. Nos. 3,237,990 and 3,232,670, Robbins et al. Such machines have a rotary head of about the diameter desired for the tunnel. Each rotary head can be equipped with a number of rotatable cutters which have their axes of rotation in radial alignment with the rotary head. These cutters are positioned in a pattern which will enable them to circumferentially fracture the area of the earth or rock face in front of the rotary head during rotation of the head.

Each cutter has a circumferential cutting edge which is composed of very hard metal. As the rotary head is rotated it is advanced (against the earth structure through which the tunnel is being bored) by means of hydraulic rams. Contact betweenthe circumferential cutting edge of the cutter and the earth or rock against which it impinges results in fracturing and dropping of such earth or rock to the floor of the bore where it is gathered up and dumped on to a belt which carries it to the rear of the advancing machine.

During operation of the machine the cutters and the bearings on which they are mounted are subjected to very great stress. This is particularly true when the machine is attacking a very hard rock structure. When this occurs the cutters are placed under severe strain and their life is apt to be quite short. In some formations the circumferential cutting surface will fail in less than 100 feet of boring.

SUMMARY OF THE INVENTION The present invention has as its object to provide a more efficient and longer lasting cutter tool. This is accomplished by prestressing the circumferential cutting edge of the cutter tool in order to make it better able to withstand the very severe compressive shocks applied to the tool during operation of the boring machine.

The prestressing is accomplished by providing the inner surface of the ring with a tapered cross-sectional configuration. A first annular support member engages one of the tapered inner-surfaces and a second annular support member engages the other tapered surface. These annular support members may be drawn toward each other to exert a hoop stress on the cutting ring, thereby placing it in a prestressed condition. Thus prestressed the cutter ring is capable of withstanding greater compressive forces as hard rock surfaces are encountered than is the case if the cutter ring is not prestressed.

DESCRIPTION OF THE DRAWING In the drawing FIG. 1 is a view, partly in section, of a cutter tool constructed in accordance with this invention.

FIG. 2 is an alternative embodiment shown in cross section of the cutter ring portion of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The cutter tool of this invention consists of a shaft on which is mounted a pair of sleeves l l and end plates 12. The sleeves l1 and end plates 12 are removably but not rotatably mounted on the shaft 10. While the sleeves l1 and end plates 12 are illustrated with a circular configuration they can have other configurations which will enable them to be readily and firmly mounted upon the rotary head of a tunnel-boring machine.

A pair of bearings 13 and 13a are mounted upon the shaft 10. These may be roller bearings. They bear the brunt of the forces applied to the cutting tool during operation and must be both rugged and well lubricated. Mounted upon the bearing 13 is an annular support member 14. A similar annular support member 14a is mounted upon the bearing 13a. The support members 14 and 14a are spaced a short distance from each other and are axially movable along the shaft 10. The support members 14 and 14a are connected to each other by means of a number of bolts 15 which are spaced around a circumference. Each bolt 15 threadably engages one of the members 14 and 14a. Where the member 14 is threaded for engagement with a bolt 15 the member 14a is threaded for the bolts immediately adjacent thereto.

The support member 14 has an annular inclined surface 16 and the support member 14a a mirror-image annular inclined surface 16a. Thus, when the bolts 15 are tightened the surfaces 16 and 16a are drawn toward each other to exert pressure against a cutting ring or disc 20.

The ring 20 is the portion of the cutter tool which engages the earth or rock which it is desired to remove. It is applied with great force and must be composed particularly along its leading edge of a material which has a Rockwell C hardness of at least 60. Alloy steels are satisfactory for this purpose. Preferred materials are cemented carbides such as cobalt-cemented tungsten carbide or titanium carbide. The ring 20 may be composed of a single alloy or, as shown in FIG. 2, may consist of several closely engaging members. The device will first be described to cover the embodiment of FIG. 1 wherethe ring 20 is a single solid member.

In cross section the ring 20 has roughly the configuration formed by two triangles placed base-to-base. On the outer side of the ring this provides a cutting edge 20a and slopedadvancing surfaces 20b and 20c. On the inner side the ring 20 has surface 20d in engagement with surface 16 of support member 14 and surface 20a in engagement with surface of support member Tightening of bolts 15 draws the support members 14 and 14:: toward each other with the result that the surfaces 16 and 16a apply hoop stresses to the ring 20. The ring 20 is thus placed under hoop tension which enables it to better withstand the tremendous compressive forces applied to it during operation of the tunnelboring machine. Extremely hard materials are customarily rather weak in tension so care must be exercised are axially movable by means of .a plurality of set screws 18 in order to hold clearances to a minimum.

The ring 20 derives certain advantages from having the composite construction illustrated in FIG. 2. In this construction an outer ring 20f is composed of a hard material such as tungsten carbide while the inner rings 20g and 20h are composed of a less hard material such as mild steel. The interior sides of the ring 20f have a cross-sectional tapered configuration to provide a side 20] corresponding to the side 20d and a side 20k corresponding to the side 20c. A slight gap is left between the portions 20g and 20h. Thus, when the supporting members 14 and 14a are drawn toward each other the portions 203 and 20h are placed under compression rather than tension. The portion 20f, however, is placed under tension. Since this is the portion of the ring which is subjected to greatest compressive force during operation of the machine, the prestressed condition is applied where it will confer the greatest benefit.

In the drawing clearances between parts have been exaggerated for purposes of illustration. All parts are made to very close tolerances in order to minimize clearances between parts which might otherwise provide an entryway for abrasive dust particles which would reduce the operating life of the cutting tool.

While the invention has been described with reference to certain specific embodiments, it is obvious that there may be variations in structure which properly fall within the scope of the invention. Accordingly, the invention should be limited in scope only as may be necessitated by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. a cutter tool for an earth-boring machine comprismg a cutter ring, said ring having a circumferential cutting edge on its outer surface composed of a metal having a Rockwell C hardness of at least 60 and an inner surface of tapered cross-sectional configuration;

a first annular support engaging one of said inner tapered surfaces;

a second annular support engaging the other of said inner tapered surfaces;

means for drawing said annular supports toward each other to apply hoop stresses to said cutter ring; bearing and shaft means for rotatablymounting said cutter ring and annular supports on said shaft; and means for mounting said shaft on an earth-boring machine.

2. A cutter tool as claimed in claim 1 wherein the cutter ring is composed entirely of cemented tungsten carbide. I

3. A cutter tool as claimed in claim 1 wherein the inner portion of the cutter ring is composed of steel.

4. A cutter tool for an earth-boring machine comprising a shaft;

means fixedly mounted on each end of said shaft for mounting said tool on an earth-boring machine;

a bearing positioned on said shaft;

and an assembly positioned on said bearing to be rotatable with respect to said shaft, said assembly consisting of a cutter ring composed of a metal having a Rockwell C hardness of at least 60 and a circumferential cutting edge on its outer surface, an inner surface of tapered cross-sectional configuration, and a pair of annular support members movable toward and away from each other, each support member having a surface in contact with a different one of said tapered inner surfaces whereby movement of said support members toward each other applies hoop stresses to said cutter ring.

5. A cutter tool as claimed in claim 4 wherein the cutter ring is composed entirely of cemented tungsten carbide.

6. A cutter tool as claimed in claim 4 wherein the inner portion of the cutter ring is composed of steel. 

1. A CUTTER TOOL FOR AN EARTH-BORING MACHINE COMPRISING A CUTTER RING, SAID RING HAVING A CIRCUMFERENTIAL CUTTING EDGE ON ITS OUTER SURFACE COMPOSED OF A METAL HAVING A Rockwell C hardness of at least 60 and an inner surface of tapered crosssectional configuration; a first annular support engaging one of said inner tapered surfaces; a second annular support engaging the other of said inner tapered surfaces; means for drawing said annular supports toward each other to apply hoop stresses to said cutter ring; bearing and shaft means for rotatably mounting said cutter ring and annular supports on said shaft; and means for mounting said shaft on an earth-boring machine.
 2. A cutter tool as claimed in claim 1 wherein the cutter ring is composed entirely of cemented tungsten carbide.
 3. A cutter tool as claimed in claim 1 wherein the inner portion of the cutter ring is composed of steel.
 4. A cutter tool for an earth-boring machine comprising a shaft; means fixedly mounted on each end of said shaft for mounting said tool on an earth-boring machine; a bearing positioned on said shaft; and an assembly positioned on said bearing to be rotatable with respect to said shaft, said assembly consisting of a cutter ring composed of a metal having a Rockwell C hardness of at least 60 and a circumferential cutting edge on its outer surface, an inner surface of tapered cross-sectional configuration, and a pair of annular support members movable toward and away from each other, each support member having a surface in contact with a different one of said tapered inner surfaces whereby movement of said support members toward each other applies hoop stresses to said cutter ring.
 5. A cutter tool as claimed in claim 4 wherein the cutter ring is composed entirely of cemented tungsten carbide.
 6. A cutter tool as claimed in claim 4 wherein the inner portion of the cutter ring is composed of steel. 